I have a strategy guide for playing japan… I will bump it for ya.
You should buy transports regardless of what you are doing, you need boats to take control of dutch islands and to take calcutta.
Also try doing J1 DOW, it will accelerate your gameplay experience and most people have more fun doing that - it is fun for everyone. If you are playing a multiplayer and you are not going to war on the first round with Japan… people will lose interest in the game fast. There is no real advantage to postponing a declaration of war, at least from the perspective of Japan, unless you have something better to do like kill a bunch of infantry that decided to stack up on amur, which is rarely the case. Maybe the Europe half needs usa out of the war while it goes sea lion, which could cause you to wait… most of the time I still J1 DOW even if I do go sea lion.
The axis have it good like that. Also most of the fun is in the pacific in global. Maybe if the Russians started with 2 additional armor and a bomber would I find the europe half interesting.